Broadband communication system for mobile users in a satellite-based network

ABSTRACT

A satellite-based communications system operating at high data rates includes a plurality of satellites each having uplink and downlink antennas for transmitting and receiving a plurality of signals utilizing a plurality of spot beams to and from a plurality of coverage areas at a predetermined range of frequencies. The system also includes a plurality of user terminals for transmitting and receiving signals to and from the plurality of communications satellites at the predetermined range of frequencies and at one of the first plurality of data rates. Each of the user terminals having a steerable antenna for tracking relative movement of each of the user terminals with respect to each of the plurality of communications satellites and for tracking movement of each of the plurality of communications satellites in order to maintain communications with the plurality of communications satellites.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/771,862 entitled “Broadband Communication System for Mobile Users ina Satellite-based Network” filed on Feb. 3, 2004, now U.S. Pat. No.7,324,056, which is a Continuation-in-Part of U.S. Ser. No. 08/867,197,filed Jun. 2, 1997, which is now U.S. Pat. No. 6,032,041, issued Feb.29, 2000; the subject matter of each being incorporated herein byreference.

TECHNICAL FIELD

This invention relates to methods and systems for providing broadbandcommunications to mobile users in a satellite-based communicationsnetwork.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Wired terrestrial systems offer communications at high data rates, butonly while the user is sitting behind a computer. As soon as the usergoes to a conference room, walks outside an office building, gets into acar, or drives to a park, the connection is lost. Mobility, however, canbe supported in one of two ways, namely terrestrial-based wirelessnetworks or satellite-based communications systems.

Terrestrial-based wireless networks provide voice or data communicationsbetween a mobile user and a fixed user or to other mobile users, as wellas communications for modem-equipped computers and other similar devicessuch as mobile facsimile machines. Existing wireless networks have notbeen optimized for a mix of voice, data, and video, however, despite thetrend towards multimedia traffic. Several wireless and wired standards,such as asynchronous transfer mode (ATM), are being designed to optimizemultimedia traffic. Wireless wide area networks (WANs) typically carryvoice, whereas wireless local area networks (LANs) typically carry data.Most wireless WAN traffic operates at under 19.2 kbps. Wireless LANsthat support data rates up to 10 Mbps have begun to appear, but they arelimited in range to tens of meters.

A typical terrestrial-based wireless network includes a grid of servicezones or cells, with each cell having a base station situated near itscenter. A mobile user located in a particular cell is connected to thatcell's base station through low-power radio frequency (RF)transmissions. Each base station is connected by trunk lines to othergateways, which in turn are connected by trunk lines to various othernetworks. Each of these cells requires costly infrastructure developmentand covers only a very small area. Placing a wireless base station every200 m to provide global mobile communications is a very costly andtime-consuming endeavor. In addition, the elevation angle between theuser and the base station is relatively low for terrestrial-basedwireless networks. At high frequencies, obstructions such as trees,buildings, signs, etc. can interfere with reliable communications.

To provide wireless service, satellite-based communications systems havebeen proposed which would provide world-wide fixed or low-rate (mainlyvoice) mobile coverage. These proposed systems typically include aconstellation of satellites in one orbit only, such as geostationaryearth orbit (GEO) only or non-geosynchronous orbit (NGSO) only.Communications satellites in geosynchronous orbit provide coverage inpredetermined areas on the earth from the equator. Coverage is typicallyexcluded from the oceans so that satellite capacity is not wasted onnon-populated areas. Communications satellites in geosynchronous orbit,however, provide limited coverage at higher or lower latitudes than theEquator.

Communications satellites in non-geosynchronous orbit, such as mediumearth orbit (MEO) or low earth orbit (LEO), travel relative to theEarth's rotation and typically provide high elevation angle coverage atthe higher and lower latitudes, and since they are closer to earth,propagation time delays are minimized. Non-geosynchronous communicationssatellites, however, waste satellite capacity over the oceans duringtheir orbit and currently do not support broadband service to mobileusers.

Data rates up to 19.2 kbps, as available from wireless WANs, will notmeet future data rate needs of consumers. For example, many computerusers are upgrading their wired modems to 56.6 kbps whenever possible.Such users desire a fast response from their modems even while they areaway from their desks. In addition, the nature of the information beingtransferred is changing from short, text-based electronic mail messagesto communications with embedded video clips or file attachments. Suchmedia-rich messages consume high bandwidth and communications resources,thus requiring high data rates to allow them to be transmitted andreceived within a reasonable period of time.

Thus, there exists a need for a wireless communications system thatprovides broadband communications to mobile users. There also exists aneed for an efficient satellite communications system that providesglobal communications service while maximizing the useful capacity ofthe satellites, reducing the perceived time delay, and maximizing theminimum elevation angle across latitudes.

SUMMARY

The present invention provides a broadband satellite communicationssystem providing global broadband network services to mobile users. Thesystem includes a plurality of satellites each having uplink anddownlink antennas for transmitting and receiving a plurality of signalsutilizing a plurality of spot beams to and from a plurality of coverageareas at a predetermined range of frequencies. Each of the plurality ofsatellites transmits and receives the plurality of signals at one of afirst plurality of data rates. The system further includes a pluralityof user terminals for transmitting and receiving signals to and from theplurality of communications satellites at the predetermined range offrequencies and at one of the first plurality of data rates. Each of theuser terminals have a steerable antenna for tracking relative movementof each of the user terminals with respect to each of the plurality ofcommunications satellites and for tracking movement of each of theplurality of communications satellites so as to maintain communicationswith the plurality of communications satellites.

In a further aspect of the invention, a portable antenna assembly isprovided that connects to an output port of an electronic device such asa computer or a telephone. The portable antenna assembly has a connectorcoupled to a transmission wire, which in turn is coupled to an antennaelement. The antenna element sends and receives signals from asatellite. The antenna may also include a tracking device so that thedirection of the antenna may be changed in response relative movement ofthe antenna location and the location of the satellites.

One advantage of the present invention is that power used by thesatellite system may be conserved by using a routing switch that routessignals according to their desired destination. Typically, a packetswitch is used to route signals. If the received beam is to betransmitted through to the same beam, the carrier frequency can beshifted and the signal returned through the same beam. These signalsthus bypass the packet switch. This saves energy because the packetswitch performs other operations on the signal such as demodulation,instruction reading and remodulation, each of which consumes energy. Theextra functions are unnecessary if the signal is routed through the samebeam.

In yet another aspect of the invention, the spot beams of two satellitesmay be combined on the ground to provide ubiquitous coverage over theentire land mass. If medium Earth orbit satellite orbits are used, atleast two MEO satellites are in view at any one time with the preferredconstellation.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustration purposes only and arenot intended to limit the scope of the present disclosure in any way.

FIG. 1 is a diagrammatic representation illustrating a satellitecommunications system of the present invention;

FIG. 2 is a schematic illustration of a GEO/MEO constellation ofcommunications satellites utilized in the present invention;

FIG. 3 is a schematic illustration of a GEO/Inclined GeosynchronousOrbit (IGSO) ground track of communications satellites alternativelyutilized in the present invention;

FIG. 4 is a schematic block diagram illustrating a communicationssubsystem within the satellites of the present invention;

FIG. 5 is a schematic illustration of satellite coverage using spotbeams;

FIG. 6 is a schematic illustration of an alternative constellation ofcommunication satellites utilized in the present invention;

FIG. 7 is a schematic illustration of a portable flat panel antenna thatmay be used to link an electronic device to a satellite;

FIG. 8 is an alternative embodiment of a portable antenna assemblyhaving a parabolic antenna;

FIG. 9 is a plan view of a laptop computer coupled to an antenna;

FIG. 10 is a plan view of a cellular phone coupled to an antenna;

FIG. 11 is a cutaway plan view of an automotive vehicle having acomputer coupled to antenna;

FIG. 12 is a schematic view of a switch according to the presentinvention;

FIG. 13 is a plan view of a spot beam formed according to the presentinvention; and

FIG. 14 is a schematic representation of a pair of satellites positionedover a land mass and directing communication signals to the land massaccording to the present invention.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is notintended to limit the present disclosure, application, or uses. Forpurposes of clarity, the same reference numbers will be used in thedrawings to identify similar elements. As used herein, the term modulerefers to an Application Specific Integrated Circuit (ASIC), anelectronic circuit, a processor (shared, dedicated, or group) and memorythat execute one or more software or firmware programs, a combinationallogic circuit, and/or other suitable components that provide thedescribed functionality. As used herein, the phrase at least one of A,B, and C should be construed to mean a logical (A or B or C), using anon-exclusive logical or. It should be understood that steps within amethod may be executed in different order without altering theprinciples of the present disclosure.

Referring first to FIG. 1, a communications system 10 with a typicalgeometry for practicing the present invention is diagrammaticallyillustrated. In general, the system 10 includes a plurality ofcommunications satellites both in geostationary earth orbit (GEO) 12 andin non-geostationary earth orbit (NGSO) 14 and 15. A system alsoincludes a ground station 16 for controlling and maintaining operationof satellites 12, 14, and 15, as well as user terminals in the form ofeither mobile devices 18 or portable devices 20. The system 10 alsoincludes a system access node 22 situated in each region serviced bysatellites 12, 14, and 15 which is connected by trunk lines to one ofseveral possible networks 23, e.g., local or long distance publicswitched telephone networks (PSTN), Asynchronous Transfer Mode (ATM)networks, the Internet, DirecPC (a satellite-based Internet accesssystem), or any other data or voice networks. Still further, the system10 uses information from at least one GPS satellite 24 to assist inproviding positioning information to mobile devices 18.

To provide efficient global coverage, satellites 12, 14, 15 arepositioned in two different constellations. The GEO satellites 12provide quick introduction of regional services, low cost service overselected regions, and greater capacity over high-traffic areas than aNGSO constellation. Preferably, GEO satellites 12 consist of a pluralityof satellites in geostationary orbit over high demand regions of theworld.

The NGSO satellites 14, 15 may consist of either medium earth orbit(MEO) satellites 14 or inclined geosynchronous orbit (IGSO) satellites15. Both MEO and IGSO satellites provide high elevation angle service tohigher latitudes, and add satellite diversity to mitigate shadowing andinterference effects. MEO satellites 14 reduce latency for highlyinteractive applications. The round-trip delay to a MEO satellite 14 atan altitude of 10,352.080 km is approximately 80 ms, which servesinteractive, real-time traffic well. The MEO constellation also providesa large overall system capacity at a lower complexity than does a lowearth orbit (LEO) constellation. Preferably, the MEO constellation isformed by 4 planes, with 5 satellites per plane, as shown in FIG. 2.Also preferably, the MEO constellation is at an equatorial altitude of10352 km for a 6-hour orbit that repeats its ground track approximatelyevery twenty-four hours. The repeatable ground track feature simplifiesthe complexity of the satellite payload, since it only has to store fourmaps identifying its four different orbit patterns. The repeatableground track also simplifies the sharing of spectrum with other systemsand potentially the design of the ground antenna. The satellites in eachplane are inclined by 30-60 degrees and have optimized phasing betweenplanes. This constellation allows for over 35 degree elevation tolatitudes up to 80 degrees.

The system 10 of the present invention can share the requested frequencyspectrum with a limited number of other satellite and terrestrialconstellations through satellite diversity. In the MEO implementation,dual satellite diversity exists at latitudes up to 70 degrees, whichpermits a user to switch to another satellite in view when the signalfrom its original satellite degrades due to low elevation angle,shadowing, or interference. Over 50% of the time, the MEO user seesthree satellites in the latitudes between 20 and 60 degrees. Thissatellite diversity can also allow increased capacity in a particulargeographic location.

IGSO satellites 15 may alternatively be utilized for many of the samereasons an MEO constellation is used, i.e., to provide high elevationangle coverage for higher latitudes than available through GEOsatellites, and to minimize the interference with other communicationsystems operating at the same frequency. Preferably, the IGSOconstellation consists of 4 planes of three satellites per plane, phasedby 90 degrees between planes at 55 degrees inclination. A ground trackof the IGSO satellites 14 is shown in FIG. 3. As shown in FIG. 3, IGSOsatellites 15 share an orbit slot with GEO satellites 12. That is, theconstellation of IGSO satellites 15 allows the IGSO satellite 15 to passover an arc of the GEO satellite 12. Scarce frequency spectrum can beshared between GEO satellites 12 and IGSO satellites 15. Thisconfiguration also allows an additional satellite, not part of thesystem 10 of the present invention, to be placed in the same orbit slotand provide service while operating at the same frequency, therebysharing frequency spectrum.

Each of the satellites 12, 14, 15 are preferably high power satellitesthat use a multi-panel solar array system, along with outboard radiatorpanels attached to the main body to dissipate heat generated from highpowered Traveling Wave Tubes (TWTs). A schematic block diagramillustrating a communications payload 29 within satellites 12, 14, 15 isshown in FIG. 4. Each satellite 12, 14, 15 includes a high frequencyuplink antenna array 30, a high frequency downlink antenna array 32, ahybrid switch 34, and intersatellite links 36. This architecture allowsa signal received by one satellite to be transponded directly back tothe same beam, switched to another beam, or relayed by intersatellitelinks through other satellites, forming a global network for thetransport of real-time voice and data signals.

Payload 29 operates in a predetermined frequency range, preferably inthe 50/40 GHz region (i.e., V-band), or any other similar high frequencyrange, to provide high capacity service to small user terminals. Thehigher frequencies are associated with the longer bandwidth needed tosupport users at many high rates. For example, data rates up to 2.048Mbps (equivalent to E1 rate) for portable devices 20 and up to 10 Mbps(equivalent to Ethernet rates) for mobile devices 18 can be supported.Users operating at data rates below the E1 or Ethernet levels can beaccommodated through a variety of medium access control protocols suchas TDMA.

Uplink antenna array 30 and downlink antenna array 32 at the satellitereceive and transmit spot beams carrying signals at a predeterminedrange of frequencies. Narrow spot beams allow a greater power to beeffectively received and transmitted in the area they cover and enablevery small antennas for mobile devices 18. A single satellite antennacan produce many spot beams. Not only do satellites with multiple narrowbeam antennas provide a higher radiated power to a covered area, but thesame frequency can also be reused several times for different portionsof the earth, resulting in more efficient use of scarce frequencyallocations.

In the present invention, a surface, or area, such as the ContinentalUnited States (CONUS), which receives communications services of thepresent invention is divided into a plurality of coverage areas 43, asshown in FIG. 5. Uplink and downlink antennas 30, 32, respectively, cansupport a predetermined number of coverage areas, e.g., 200. However, asubset of the plurality of coverage areas 43 is chosen to be used byuplink and downlink antenna arrays 30, 32, respectively, to supportcommunications services in selected metropolitan areas having heavytraffic. As an example, the Los Angeles area can be served by one highcapacity beam, (e.g., Beam 1) while other areas, such as Phoenix andDetroit, are served by other high capacity beams (e.g., Beams 40 and60). This configuration is controlled by beam selection commands sent byground station 16. Thus, the spot beams formed by GEO satellites 12 aresemi-fixed in position, until reconfigured at a later date. It ispossible to have the beams “hop” across various regions in a non-uniformmanner, so as to dwell the majority of the time over high-demand areas,but also to serve low-demand areas at predetermined times. Thus,available satellite resources, such as weight and power, are optimized.The MEO spot beams are reconfigured dynamically as the MEO satellite 14travels.

GEO satellites 12 preferably transmit the spot beams utilizing amultibeam antenna array. Many small feed horns are positioned so thattheir signals are reflected in narrow beams by a dish portion of theantenna. For the MEO satellites 14 and the IGSO satellites 15, the spotbeams are formed by steerable phased array antennas.

When traffic is received from a source beam that is destined for thesame beam, hybrid switch 34 allows the traffic to be sent throughbent-pipe repeater 40 down to the same beam with only a carrierfrequency translation. Alternatively, the traffic through bent-piperepeater 40 can be routed to one or more hub beams. The system accessnode 22 in the receiving beam receives the information and routes thetraffic to its intended destination either through the wired network 23or back through the satellite. This configuration allows for fullflexibility in routing traffic to its ultimate destination, whilereducing the satellite switch size, power draw, and mass.

When traffic is received from a source beam that is destined for adifferent beam, hybrid switch 34 routes the traffic through full digitalpacket switch 41. Full digital packet switch 41 demodulates incomingpackets, reads the headers and decodes the packets, routes the packetsto their destination beams, encodes the packets and remodulates thepackets. Alternatively, an error switch can be flown on the satellite,with appropriate reading of the header determining the destination beam.This feature allows direct connections between user terminals 18, 20, aswell as bypass of the terrestrial network for other connections. Apacket arrangement allows a user to be charged for services based on bittraffic rather than a more expensive interconnect time.

Thus, hybrid switch 34 allows routing from one beam to another andbypasses full digital packet switch 38 for bent-pipe connections topredetermined beams. The system 10 allows controller 39 at the satelliteto control real-time traffic on satellites 12, 14, 15 rather than on theground, so as to reduce transmission delay, congestion and complexityand cost of the total system.

The logic determines whether a signal should be sent through thebent-pipe repeater 40 or through the digital packet switch 41 can beimplemented in many ways. One method would be to use special frequencybands for the transmission of bent-pipe traffic. In this method, theuser terminal 18,20 transmits the signal at a specific frequencydepending on whether or not signal is to be bent-pipe routed back to thesame beam as the source location of the signal, or packet-switched to adifferent beam. The satellite, detecting traffic on these frequencies,knows to route the traffic through the bent-pipe repeater or to thepacket switch via hard-wired connections. Another method would be to usespecific time slots for bent-pipe traffic and other time slots forpacket-switched traffic. In this method, the table of which time slotsare used for bent pipe traffic and which time slots are used forpacket-switched traffic would be stored in a routing table 38. Thisrouting table 38 can be updated by commands sent by ground station 16via a controller 39 onboard the satellite. Thus, the signals can bedifferentiated at the satellite without the need for demodulation,reducing the satellite switch size, power consumption, and mass.

The user terminal 18,20 can transmit both types of signals; those meantto be bent-piped back to the same beam or packet-switched to a differentbeam. There are various methods for the user terminal 18,20 to selectwhich type of signal to transmit. One method is to have the terminalautomatically select the type of signal based on the application; localphone calls, for instance, might all be sent as bent-pipe signals,whereas web browsing might automatically use the packet-switched signalto more quickly access distant web servers. Another method is to havethe user select whether his connection is to be back to the same beam orto a different beam.

The data rates vary depending upon the user terminal 18, 20 and whetheror not rain is present. When there is no rain present, mobile devices 18support maximum bit rates of 10 Mbps, while portable devices 20 supportmaximum bit rates of 2 Mbps. The minimum data rate supported is 4 kbpsfor compressed voice traffic. In heavy rain periods, user terminals 18,20 fall back to a lower data rate to mitigate the effects of additionalsignal attenuation caused by rain. In this lower data rate mode, mobiledevices 18 support bit rates of up to 2.5 Mbps, while portable devices20 support bit rates of 500 kbps. These data rates can carry a range ofservices, including voice, high quality video, image downloads, andinternet/intranet browsing. The control of the data rate can beaccomplished by one of several possible methods. Preferably, the datarate is controlled on-board the satellite by having the controller 39detect degraded performance in a given service area 43 and automaticallyadjust the information data rate. The data rate is adjusted by includingmore error correction bits in the signal which increases the reliabilityof the message while reducing the effective data rate.

Because weather conditions are local, a portion of the beam (Beam #1)serving the Los Angeles area might be operating in the clear mode, whileanother portion of the same beam may be experiencing rain. In order tominimize the impact of lower data rates to the area affected by therain, the area where lower data rates must be used is localized at anypoint in time. A user learns of the current data rate through theconnection setup procedure. If the weather changes during theconnection, the satellite controller 39 sends a broadcast informationpacket informing the affected users of the data rate change. Userterminals 18, 20 then automatically switch to the lower data rate.

Intersatellite links 36 are included so that traffic from one satellitecovering a particular region or selected metropolitan areas can belinked to a second satellite covering the same or other areas andregions. Intersatellite links 36 also permit seamless handoffs oftraffic as one NGSO satellite leaves a region and another enters.Intersatellite link 36 may be an optical (or laser) link operating inthe 1.55 micron region via two 9 inch laser-telescope assemblies 71,73.Alternatively, intersatellite link 36 may be a radio frequency (RF) linkoperating in the 60 GHz region.

As discussed above, each of the satellites 12, 14, and 15 are also incommunication with ground station 16. Ground station 16 has twofunctions. A satellite control function manages the health and status ofall the satellites 12, 14, 15 and maintains their orbits. A networkoperations control function provides resource management, faultmanagement, accounting and billing information. Ground station 16 ispreferably placed in low-rain regions of the world so as to provideline-of-sight communications with each of the satellites 12, 14, and 15.

The system 10 further includes mobile devices 18 or portable devices 20.Mobile devices 18 provide safety, external navigation, productivity andentertainment services to mobile vehicles, such as cars, trucks,airplanes, trains or boats. Utilizing GPS 24, tracking information andlocation-dependent services can be provided to mobile device 18. Mobiledevice 18 is preferably a conformal tracking phased array antennamounted to the roof of the mobile vehicle so as to maintaincommunication with each of satellites 12, 14, and 15 even though mobiledevice 18 is in motion. Mobile device 18 is preferably no larger than 50cm×50 cm.

Portable devices 20 allow a user to stay connected to a variety ofservices anywhere in the world. Portable device 20 is a notebook-sizeddevice, preferably no larger than 20 cm×30 cm in size, that isconfigured to be connected to a variety of electronic devices whichwould otherwise use a wired modem connection. As with mobile devices 18,portable devices 20 includes a tracking antenna, such as an electronicphased-array antenna, to communicate with any of the satellites 12, 14,and 15.

System access node 22 of the present invention provides end users atransparent connection to terrestrial networks 23. System access node 22includes an antenna, such as a fixed parabolic antenna or a mechanicallysteered or phased array antenna, to communicate with each of thesatellites 12, 14, and 15. System access node 22 demodulates thereceived signals, and routes the traffic through the terrestrial network23 to their ultimate destinations. By providing a global communicationsmesh, and by interfacing to existing terrestrial networks, the system 10of the present invention will be an integral and defining part of theGlobal Information Infrastructure (GII), and part of the U.S. NationalInformation Infrastructure (NII).

The satellite communications system of the present invention serves theincreasing number of people on-the-go who desire voice and highdata-rate, interactive data connections from anywhere. Using either theportable or mobile device, users are able to stay connected to a varietyof networks such as the internet, wide and local area networks, home andoffice computers, ATM networks, and the terrestrial phone system.

In one possible implementation, the capacity to a mobile user 18 is 9.75Gbps per GEO satellite 12 and 5.12 Gbps per MEO satellite 14. The MEOconstellation can support up to 102 Gbps worldwide. With a total of 28satellites in both MEO 14 and GEO 12, the total mobile system capacityjumps up to 190 Gbps worldwide. The network is capable of supporting awide variety of data rates, ranging from 4 kbps for compressed voicetraffic up to 10 Mbps for Ethernet speeds. The number of users at eachdata rate will vary, and the corresponding total number of users thatthe network can support will vary accordingly.

The system 10 of the present invention can include, or be combined with,other systems to enable increased capacity over high-population areasand ubiquitous coverage over lower-population areas and to provide abackup connection at a lower frequency to maintain the communicationslink in rain conditions. This can be accomplished by having the othersystems transmit a wide area beam surrounding the narrow spot beams toprovide service to the remote areas not covered by the spot beams. Thedata rates in these areas, however, would typically be lower than thedata rates of the present invention.

Referring now to FIG. 6, system 10 as described above contains NGSOsatellites such as MEO satellites 14 or IGSO satellites 15 as well asGEO satellites 12. System 10, however, may also be extended to includelow earth orbit (LEO) satellites 16. At present, the LEO orbit 16 is nota cost effective satellite system. LEO satellite systems, due to theirclose proximity to the earth, typically comprise several more satellitesin their orbital path than with MEO satellite systems. By providingseveral more LEO satellites or several more MEO satellites in acommunications system, higher elevation angles may be achieved. Thehigher elevation angles reduce shadowing effects. If demand increases asprojected, MEO satellites 14, IGSO satellites 15, and LEO satellites 16,along with GEO satellites 12, may cooperate to provide direct coverageand sufficient capacity for predetermined areas on the earth's surface.One advantage of the system is that as the various satellites travelwith respect to the earth's surface, the spot beam pattern may bealtered to suit the particular land mass and usage requirements. Thesechanges will be further described below.

Referring now to FIG. 7, an antenna assembly 50 is shown, which issuitable for coupling to an electronic device. Antenna assembly 50 has ahousing 52 which is sized to permit easy transportation of the antennaassembly. In a preferred embodiment, antenna assembly 50 is preferablyless than 20 cm by 30 cm. Antenna assembly 50 has a connector 54 sizedto be received within an output port of an electronic device. Connector54 may, for example, be the size of a phone jack and coupled to a modemport of a computer. Connector 54 is also coupled to an antennacontroller 56 by a transmission line 58. Transmission line 58 alsoextends between antenna controller 56 and a motor 60. Motor 60 iscoupled to an antenna 62 and used to position the antenna 62 to receiveand send satellite communications.

Antenna controller 56 is preferably microprocessor based and receivessignals from antenna 62 to allow motor 60 to properly position antenna62. Commonly, satellites generate beacons that may be used to properlyposition the antenna 62.

In order to position the antenna 62, it should be aimed skyward. Beaconsignals are received through the antenna 62 and the controller 56 thencalculates the desired direction for the antenna. The desired directionis preferably toward one of the satellites in view.

Antenna 62 is preferably a flat panel antenna and may be, for example, aphased array antenna or is mechanically steered and rotated by motor 60,to its desired position, where the shape of the beam may beelectronically generated through antenna controller 56. Thus, the beamis a mechanically steered electronically shaped beam.

Referring now to FIG. 8, the same reference numerals are used toidentify the same components as in FIG. 7. The difference between FIG. 8and FIG. 7 is that the antenna of FIG. 7 has been replaced by aparabolic dish antenna 64. Parabolic dish antenna 64 is preferablypositioned in a similar manner to that of antenna 62, above. Also,housing 52 is preferably sized to facilitate portability. Parabolic dishantenna 64 may be foldable or disassemble to facilitate compact storagewhen not in use.

Referring now to FIG. 9, one example of a use for the portable antennais illustrated. Antenna assembly 50 may be coupled to a laptop computer66 through connector 54. In this embodiment, antenna controller 56 ofFIGS. 7 and 8 may be incorporated directly into the laptop computer 66.Thus, motor 60 may be positioned through the microprocessor within thecomputer.

Referring now to FIG. 10, another application for use of an antennaassembly 50 is illustrated. In this system, the antenna assembly 50 iscoupled to a cellular phone 68. In addition to, or exclusive from, itscapability to communicate with terrestrial-based cell sites, cellularphone 68 may use antenna 62 to communicate directly with a satellite.Cellular phone 68 may also incorporate the antenna controller functiontherein. However, due to the ever decreasing size of cellular phones, itis more likely that a commercial embodiment would position the antennacontroller external to the cellular phone 68.

Referring now to FIG. 11, the antenna assembly 50 may be coupled to theexterior or interior of a vehicle such as a car, airplane, train, orship. As illustrated, vehicle 70 is a car. Antenna assembly 50 iscoupled to an electronic device 72 located within the vehicle 70.Electronic device 72 may be, for example, a cellular phone or computerthat is directly wired into the vehicle. Electronic device 72 may alsobe a navigation device that uses the satellite for location of thevehicle. In an automotive vehicle, antenna controller 56 may beincorporated in one of several microprocessors onboard the vehicle.

Referring now to FIG. 12, a hybrid switch 34 such as that describedabove is illustrated in further detail. Hybrid switch 34 allows power tobe conserved, as will be described below. A controller 74 controls thevarious functions of hybrid switch 34. A receiver 76 is coupled tocontroller 74 and receives a transmission from a satellite.

Controller 74 is coupled to a lookup table 78 and input router 80.Although illustrated as two separate components, controller 74 and inputrouter 80 may be combined. Likewise, if controller has sufficientmemory, the lookup table 78 may also be enclosed within the controller74. Controller 74 analyzes the signal to determine whether the signal isdestined for the same beam or whether the signal is destined for anotherbeam. This may be accomplished without demodulating the signalinitially. Lookup table 78 may be used to find the various types ofsignals and determine their destinations based merely on the unmodulatedsignal itself. Input router 80 controls the destination of the receivedsignal and is coupled to a bent pipe repeater 82 and a digital packetswitch 84.

Bent pipe repeater 82 has a carrier frequency shifter 86 and an output88. If the received signal is to be transmitted back along the same beamfrom which it was received, input router 80 routes the received signalto bent pipe repeater 82. Repeater 82, through carrier frequency shifter86, merely shifts the carrier frequency of the received signal so thatthe received signal may be retransmitted down the same beam.

If the received signal is to be transmitted to several signals orthrough a beam different from which it was received, input router 80routes the input signal to digital packet switch 84. Digital packetswitch 84 has a demodulator 90, an instruction reader 92, a beam router94, and a remodulator 98. The received signal is demodulated indemodulator 90. This allows the instruction reader 92 to read any headerinformation contained on the received signal as to the destination ofthe received signal. Instruction reader 92 provides beam router 94 withthe information required so that beam router 94 may properly route thereceived signal to the proper beam to be transmitted back to the earth.Prior to transmission, however, remodulator 98 modulates the previouslydemodulated signal. Remodulator 98 may remodulate the demodulated signalwith various carrier frequencies depending on the beam through which thesignal is transmitted.

Referring now to FIG. 13, a spot beam 100 is divided into nine segmentslabeled A through I. A satellite may be capable of independentlycontrolling the data rates of the various areas of spot beam 100. Forexample, if area C is in rain, a lower data rate may be applied to thatarea. The other areas of spot beam 100, that is A, B, and D through I,if no rain is present, may all be operated in a non-affected (clear)data rate. One possible implementation provides transmitting atdifferent power levels on each of frequency carrier segments A throughJ.

Referring now to FIG. 14, a pair of satellites 102 and 104 arepositioned over a land mass 106, and a plurality of spot beams 108 areillustrated. Spot beams 108 from the two satellites 102 and 104 maycombine to ubiquitously cover the land mass 106. Satellites 102 and 104may have a sufficient quantity of spot beams 108 to allow overlappingcoverage in various areas of land mass 106. This is particularly usefulif one area of the country has a particularly high traffic volumethrough one of satellites 102 or 104. In certain situations, spot beams108 may directly overlap at a common area 110. Although one common areais illustrated, several common areas 110 may be applied over highlypopulated regions of the country such as Los Angeles or New York.

While the best modes for carrying out the invention have been describedin detail, those familiar with the art to which this invention relateswill recognize various alternative designs and embodiments forpracticing the invention as defined by the following claims.

Those skilled in the art can now appreciate from the foregoingdescription that the broad teachings of the disclosure can beimplemented in a variety of forms. Therefore, while this disclosureincludes particular examples, the true scope of the disclosure shouldnot be so limited since other modifications will become apparent to theskilled practitioner upon a study of the drawings, the specification andthe following claims.

1. A system for communicating with a satellite comprising: an electronicdevice having a communications port; an antenna controller coupled tosaid electronic device; and a portable satellite antenna coupled to saidcommunications port for coupling said electronic device directly to thesatellite.
 2. A system as recited in claim 1 wherein said electronicdevice comprises a laptop computer.
 3. A system as recited in claim 1wherein said electronic device comprises a computer in an automotivevehicle.
 4. A system as recited in claim 3 wherein said automotivevehicle comprises an airplane.
 5. A system as recited in claim 3 whereinsaid automotive vehicle comprises a car.
 6. A system as recited in claim3 wherein said automotive vehicle comprises a boat.
 7. A system asrecited in claim 3 wherein said automotive vehicle comprises a train. 8.A system as recited in claim 1 wherein the electronic device is mobile.9. A system as recited in claim 1 wherein the electronic device isportable.
 10. A system as recited in claim 1 wherein the antenna isdisposed within an antenna housing.
 11. A system as recited in claim 10wherein the housing comprises an antenna controller therein.
 12. Asystem as recited in claim 11 wherein the housing comprises motortherein.
 13. A system as recited in claim 12 wherein said controllercontrols the motor to mechanically steer the beam and the antennacontroller electronically shapes the beam.
 14. A system as recited inclaim 1 wherein the antenna comprises a phased array antenna.
 15. Asystem as recited in claim 1 wherein the electronic device comprises acellular phone.
 16. A system as recited in claim 1 wherein the antennacomprises a parabolic antenna.
 17. A satellite system as recited inclaim 1 wherein the antenna is coupled to a connector for coupling theantenna to the communication port.
 18. A satellite system as recited inclaim 17 further comprising a transmission wire disposed between theconnector and the antenna.
 19. A system comprising: an electronic devicehaving a communications port; a connector; a transmission wire coupledto said connector; and an antenna assembly comprising, a phased arrayantenna element coupled to said transmission wire, said antenna elementsending and receiving signals from said satellite; a motor coupled tothe antenna element; and an antenna controller coupled to said motor forcontrolling a position of said phased array antenna element through saidmotor; said phased array antenna element generating a mechanicallysteered electronically shaped beam.
 20. A system as recited in claim 19wherein the electronic device is mobile.
 21. A system as recited inclaim 19 wherein the electronic device is portable.
 22. A system asrecited in claim 19 wherein said electronic device comprises a laptopcomputer.
 23. A system as recited in claim 19 wherein said electronicdevice comprises a cellular phone.
 24. A system as recited in claim 19wherein said electronic device comprises a computer in an automotivevehicle.
 25. A system as recited in claim 24 wherein said automotivevehicle is one from the group consisting of an airplane, a car, a boat,and a train.